CN102685638B - Method and apparatus for outputting audio signal - Google Patents

Abstract

A method and device for outputting an audio signal are provided. The audio signal output device includes: a pulse width modulation (PWM) unit, which generates a carrier signal, compares the signal level of the carrier signal and the signal level of the audio signal, and generates a PWM signal based on the comparison result; a controller, based on the level of the audio signal , control the PWM unit to change the signal shape of the carrier signal to adjust the duration of the logic high level of the PWM signal; the switching power supply unit amplifies the PWM signal generated by the PWM unit and outputs the amplified PWM signal.

Description

Method and device for outputting an audio signal

This application claims priority to Korean Patent Application No. 10-2011-0021045 filed with the Korean Intellectual Property Office on March 9, 2011, the disclosure of which is hereby incorporated by reference in its entirety.

technical field

Apparatuses and methods consistent with exemplary embodiments relate to outputting audio signals, and more particularly, to outputting audio signals to increase operating speed.

Background technique

Audio power amplifiers (amps) receive audio signals and output audible signals, and audio power amplifiers are generally classified as Class A, Class B, Class AB, and Class D. Here, class D power amps are widely used because deterioration in amplification efficiency is reduced compared to class A power amps, class B power amps, and class AB power amps. Class D power amps switch audio signals by converting them into pulse width modulated (PWM) signals. Class D power amps are also known as digital amplifiers.

Digital amps are widely used because of features such as little data conversion loss and 100% theoretical amplification efficiency. In such digital amps, it is important to output the incoming audio signal according to the maximum output power without generating signal distortion.

Contents of the invention

One or more exemplary embodiments provide a method of outputting an audio signal for quickly adjusting an output gain of an audio signal without delay, and an apparatus for outputting an audio signal by using the method.

One or more exemplary embodiments also provide a method of outputting an audio signal for adjusting an output gain of an audio signal while minimizing deterioration of audio quality, and an apparatus for outputting an audio signal by using the method.

According to an aspect of an exemplary embodiment, there is provided an audio signal output device, including: a pulse width modulation (PWM) unit generating a carrier signal, comparing the signal level of the carrier signal with the signal level of the audio signal, and based on the comparison As a result, a PWM signal is generated; the controller, based on the level of the audio signal, controls the PWM unit to change the signal shape of the carrier signal to adjust the duration of the logic high level of the PWM signal; the switching power supply unit amplifies the PWM signal generated by the PWM unit and Output amplified PWM signal.

When the level of the audio signal is higher than a predetermined standard level, the controller may control the PWM unit to change the signal shape of the carrier signal to reduce the duration of the logic high level of the PWM signal.

When the level of the audio signal is lower than a predetermined standard level, the controller may control the PWM unit to change the signal shape of the carrier signal to increase the duration of the logic high level of the PWM signal.

The controller may further include a storage unit storing information on a signal shape of the carrier signal corresponding to a level of the audio signal.

The controller may control the PWM unit to change the signal shape of the carrier signal to adjust the duration of the logic high level of the PWM signal for each signal level period of the audio signal having different audio signal level ranges.

The controller may control the PWM unit to change the signal shape of the carrier signal to reduce the duration of the logic high level of the PWM signal during the first time period when the zero crossing of the audio signal occurs.

The controller may control the PWM unit to change the signal shape of the carrier signal to increase the level of the PWM signal during a second time period in which the level of the audio signal is equal to or higher than the upper limit of the first time period and lower than or equal to a predetermined standard level. Duration of logic high level.

The controller may control the PWM unit to change the signal shape of the carrier signal to reduce the duration of the logic high level of the PWM signal during the third time period when the level of the audio signal is equal to or higher than the predetermined standard level.

The audio signal output device may further include: a loop filter to detect an output level of the amplified PWM signal, and monitor whether the amplified PWM signal exceeds a maximum output level.

The controller may receive the monitoring result from the loop filter, and when the level of the amplified PWM signal exceeds the maximum output level, the controller may change the signal shape of the carrier signal to reduce the duration of the logic high level of the PWM signal.

According to an aspect of another exemplary embodiment, there is provided a method of outputting an audio signal, including: detecting a level of the audio signal; generating a carrier signal having a signal shape changed based on the detected level of the audio signal, to adjusting the duration of the logic high level of the PWM signal; comparing the signal level of the carrier signal and the signal level of the audio signal; generating a PWM signal based on a result of the comparison; amplifying the PWM signal and outputting the amplified PWM signal.

Description of drawings

The above and other aspects will become more apparent from the detailed description of exemplary embodiments with reference to the accompanying drawings, in which:

1 is a block diagram of an audio signal output device according to an exemplary embodiment;

2 is a detailed block diagram of a pulse width modulation (PWM) unit of FIG. 1, according to an exemplary embodiment;

FIG. 3 shows an example of a carrier signal and a PWM signal generated by the PWM unit of FIG. 2 according to an exemplary embodiment;

FIG. 4 shows an example of a carrier signal and a PWM signal generated by the PWM unit of FIG. 2 according to another exemplary embodiment;

FIG. 5 shows an example of a carrier signal and a PWM signal generated by the PWM unit of FIG. 2 according to another exemplary embodiment;

6 shows in detail an example of a carrier signal and a PWM signal generated by the PWM unit of FIG. 2 according to an exemplary embodiment;

7 is a detailed block diagram of an audio signal output device corresponding to the audio signal output device of FIG. 1, according to an exemplary embodiment; and

FIG. 8 is a flowchart of a method of outputting an audio signal according to an exemplary embodiment.

detailed description

Hereinafter, exemplary embodiments will be described with reference to the accompanying drawings. Example embodiments may, however, be embodied in many different forms and should not be construed as limited to example embodiments set forth herein; rather, these example embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the inventive concept to those skilled in the art. In the drawings, the same reference numerals denote the same elements. Hereinafter, when an expression such as "at least one of" is placed after a listed element, it modifies all of the listed elements rather than a single listed element.

An audio amplifier system or an audio signal output device may be designed to have a maximum output based on a predetermined input level. In some cases, an audio signal output device may receive an audio signal recorded at a level higher than a standard level. In this case, the amplifier that outputs the audio signal in the audio signal output device receives an input that is too high.

When an audio signal recorded at a level higher than a standard level is reproduced at a maximum volume level, the audio signal output device performs an operation exceeding the maximum output. That is, clipping occurs. This operation may damage internal components of the audio amplifier system, such as digital amplifiers, speakers, switched mode power supplies (SMPS), and the like. For example, a speaker may be burned or cut off and therefore not be able to produce sound. Due to an increase in the internal temperature of the audio amplifier system, the circuits of the SMPS or digital amplifier may be destroyed.

In order to prevent the audio signal output device from performing an operation exceeding the maximum output, the output gain may be controlled. The digital amplifier can control the output of a signal through pulse width modulation (PWM), and can compress, expand, or boost the size of an audio signal through PWM.

Here, compressing, expanding, or boosting the size of an audio signal refers to changing the gain of an input audio signal and outputting the input audio signal.

In the analog method, the gain of the input/output audio signal may be controlled by using a variable gain amplifier (VGA) or a voltage control amplifier. On the other hand, in the digital method, the gain of the audio signal can be controlled by using a separate signal processing block that compresses or expands the signal.

As mentioned above, to control the output of the audio signal, a separate amplifier or processing block is used in addition to the components of the PWM. Accordingly, methods and apparatuses for outputting an audio signal and for minimizing distortion of the audio signal while simplifying processing blocks for controlling gain according to one or more exemplary embodiments will be described in detail.

FIG. 1 is a block diagram of an audio signal output device 100 according to an exemplary embodiment.

Referring to FIG. 1 , an audio signal output device 100 includes a controller 110 , a PWM unit 120 and a switching power supply unit 130 .

The controller 110 receives an audio signal and detects a signal level of the received audio signal. In addition, according to the detected level of the audio signal, the controller 110 controls the PWM unit 120 to change the signal shape of the carrier signal, thereby increasing or decreasing the duration of the logic high level of the PWM signal.

In detail, when the detected signal level is higher than a predetermined standard level, the controller 110 controls the PWM unit 120 to change the signal shape of the carrier signal, thereby reducing the duration of the logic high level of the PWM signal. For example, the controller 110 may detect the average signal level of the input audio signal or the peak signal level of the audio signal as the signal level of the audio signal. Also, the controller 110 may determine the signal shape of the carrier signal corresponding to the detected signal level of the audio signal, and output a change control signal for outputting the carrier signal having the determined signal shape to the PWM unit 120 .

Here, the predetermined standard level is an upper limit value for determining whether an audio signal is a signal exceeding the maximum value of the audio signal output device 100 when the signal is converted into a PWM signal or the like and finally output. output. That is, if the signal level of the audio signal exceeds a predetermined standard level, components of the audio signal output apparatus 100 may be damaged when the audio signal is finally reproduced. The predetermined standard level may be designed as a value optimized according to at least one of maximum output power, speaker performance, reliability of audio equipment, etc. that may be included in product specifications of the audio signal output device 100 .

In addition, the controller 110 may change the signal shape of the carrier signal in consideration of user preference. For example, in the case that the audio signal has a medium level, when the user wants to listen to a sound with a higher volume, the controller 110 can change the signal shape of the carrier signal so that when the level of the audio signal is equal to or lower than a predetermined standard The duration of the logic high level of the PWM signal during the time period of the level may increase. That is, the volume may increase during a period in which the level of the audio signal is equal to or lower than a predetermined standard level.

The controller 110 may store a database obtained by matching levels of audio signals and information on signal shapes of carrier signals corresponding to the levels with each other. For example, the database may be stored in a predetermined storage space (not shown) included in the controller 110 or in a separate storage space (not shown) of the audio signal output device 100 . The database may be designed or stored by at least one of a manufacturer of the audio signal output device 100 and a user.

The PWM unit 120 generates a carrier signal having a signal shape changed according to the control of the controller 110, and compares the carrier signal with an audio signal to generate a PWM signal. The detailed structure and operation of the PWM unit 120 will be described with reference to FIGS. 2 and 3 .

The switching power supply unit 130 amplifies the power of the PWM signal generated by the PWM unit 120 to generate an amplified PWM signal. For example, the switching power supply unit 130 amplifies the amplitude of the generated PWM signal according to the maximum output of the audio signal output device 100 and outputs the amplified PWM signal. When the audio signal output device 100 according to the present exemplary embodiment includes the switching power supply unit 130 for amplifying the PWM signal, it should be understood that another exemplary embodiment is not limited thereto. For example, according to another exemplary embodiment, the switching power supply unit 130 may be omitted, and the audio signal output device 100 may output the PWM signal without amplifying the generated PWM signal. In addition, it should be understood that the audio signal output device 100 according to one or more exemplary embodiments may output the PWM signal to an external speaker, another device or circuit for processing the PWM signal, and the audio signal output device 100 may use An internal speaker, etc. outputs a PWM signal.

FIG. 2 is a detailed block diagram of the PWM unit 120 of FIG. 1 according to an exemplary embodiment.

Referring to FIG. 2 , the PWM unit 120 may include a carrier signal generator 210 and a PWM signal generator 220 .

In response to the change control signal input by the controller 110, the carrier signal generator 210 generates a carrier signal corresponding to the change control signal. Carrier signals with different signal shapes are output according to the changing control signal. Here, the change control signal contains information for changing the signal shape of the carrier signal. For example, the change control signal may contain information about the signal shape of the carrier signal itself. In addition, if the carrier signal generator 210 includes information on carrier signals having a plurality of signal shapes, each change control signal may contain information for switching from a plurality of carrier signals (for example, address signals or the like) having different shapes. Read the information of a carrier signal in.

The PWM signal generator 220 receives an audio signal and a carrier signal, compares a signal level of the audio signal and a signal level of the carrier signal, and outputs a PWM signal having a pulse width modulated according to a result of the comparison. The generation of the PWM signal will be described in detail with reference to FIG. 3 .

FIG. 3 illustrates an example of a carrier signal and a PWM signal generated by the PWM unit 120 of FIG. 2 according to an exemplary embodiment.

FIG. 3 shows a case where the level of the audio signal detected by the controller 110 is a middle level such as half the amplitude. For example, when the detected level of the audio signal is a medium level, the audio signal output device may not perform an operation exceeding its maximum output. Therefore, it is not necessary to adjust the gain value of the audio signal. In addition, when the level of the audio signal is an average level, a carrier signal may be output to generate a PWM signal with a duty ratio of 50:50 maintained.

When the level of the audio signal is an average level, the gain in the case of a duty ratio of 50:50 is referred to as unity gain. Also, a carrier signal used to generate a PWM signal corresponding to a unity gain is referred to as a unity gain carrier signal.

In FIG. 3, the X-axis represents time and the Y-axis represents signal level. Also, the signal level can be in voltage (V).

Referring to FIG. 3, in response to the change control signal, the carrier signal generator 210 generates and outputs a carrier signal 310 corresponding to the change control signal.

The PWM signal generator 220 may compare the signal level of the carrier signal 310 and the signal level of the audio signal 320 . When the signal level of the carrier signal 310 is greater than that of the audio signal 320 , the PWM signal generator 220 may output the PWM signal 330 at a logic low level. In addition, the PWM signal generator 220 may output the PWM signal 330 at a logic high level when the signal level of the carrier signal 310 is lower than that of the audio signal 320 .

For example, the PWM signal generator 220 outputs the PWM signal 330 at a logic low level during a time period from t1 to t2 when the signal level of the carrier signal 310 is higher than that of the audio signal 320 . During the period from t2 to t3 when the signal level of the carrier signal 310 is lower than that of the audio signal 320 , the PWM signal generator 220 outputs the PWM signal 330 at a logic high level.

The PWM unit 120 for outputting the carrier signal changed according to the signal level of the audio signal detected by the controller 110 will be described in detail with reference to FIGS. 4 and 5 .

FIG. 4 illustrates an example of a carrier signal and a PWM signal generated by the PWM unit 120 of FIG. 2 according to another exemplary embodiment.

When the level of the audio signal is lower than the average recording level, the volume of the output sound will be low, so the user's satisfaction with the sound quality will be low. In this case, the average recording level may be an optimum audio signal level at which the corresponding audio signal output device is operable while maintaining the maximum output. As described above, an audio signal output device that outputs an audio signal by using a digital amplifier can be designed to have a maximum output based on an average recording level.

Referring to FIG. 4 , there is shown an output carrier signal corresponding to when the level of the audio signal detected by the controller 110 is lower than an average recording level. For example, the controller 110 detects a signal level of an audio signal. The detected signal level is compared with the average recording level, and if the detected signal level is determined to be lower than the average recording level, the carrier signal generator 210 can be controlled to output a gain value to increase the volume of the output signal carrier signal.

As shown in FIG. 4 , the controller 110 can control the PWM unit 120 to change the signal shape of the carrier signal 410 according to the level of the audio signal 420 to increase the duration of the logic high level of the PWM signal 430 . For example, when the level of the audio signal 420 is lower than the average recording level, or for example, when the peak level of the audio signal 420 is lower than the above-mentioned predetermined standard level, the controller 110 can control the PWM unit 120 to change the signal shape of the carrier signal 410 to increase the duration of the logic high level of the PWM signal 430 .

Compared with FIG. 3 , when the signal shape of the carrier signal 410 is close to that of FIG. 4 , the duration of the logic high level of the PWM signal 430 increases. For example, when the carrier signal 410 has the signal shape shown in FIG. 4, the PWM signal 430 is output at a logic low level during the period from t11 to t12, and at a logic high level during the period from t12 to t13. Ping is output. That is, by changing the signal shape of the carrier signal 410 according to the control of the controller 110, the gain of the audio signal 420 can be increased, and the volume of the output sound can also be increased.

FIG. 5 illustrates an example of a carrier signal and a PWM signal generated by the PWM unit 120 of FIG. 2 according to another exemplary embodiment.

When the level of the audio signal is higher than the average recording level, or when the peak level of the audio signal is higher than the above-mentioned predetermined standard level, the audio signal output device may perform an operation exceeding its maximum output and may be damaged.

Referring to FIG. 5 , as shown in FIG. 5 , the controller 110 may control the PWM unit 120 to change the signal shape of the carrier signal 510 to increase the duration of the logic low level of the PWM signal 530 according to the level of the audio signal 520 . For example, when the level of the audio signal 520 is higher than the average recording level, or for example, when the peak level of the audio signal 520 is higher than the above-mentioned predetermined standard level, the controller 110 can control the PWM unit 120 to change the signal shape of the carrier signal 510 to increase the duration of the logic low level of the PWM signal 530 .

Compared with FIG. 3 , when the signal shape of the carrier signal 510 is close to that of FIG. 5 , the duration of the logic high level of the PWM signal 530 increases. For example, when the carrier signal 510 has the signal shape shown in FIG. 5, the PWM signal 530 is output at a logic low level during the period from t21 to t22, and at a logic high level during the period from t22 to t23. Ping is output. That is, by changing the signal shape of the carrier signal 510 according to the control of the controller 110, the gain of the audio signal 520 can be reduced, and the audio signal output device can be prevented from performing an operation exceeding its maximum output.

The signal shape of the carrier signal corresponding to the level of the audio signal may be experimentally optimized and designed in consideration of the maximum output power, reliability, or the like of the audio signal output device. Also, as described above, the signal shape of the carrier signal may be designed or stored by at least one selected from the group including the manufacturer of the audio signal output device 100 and the user.

FIG. 6 illustrates an example of a carrier signal and a PWM signal generated by the PWM unit 120 of FIG. 2 according to an exemplary embodiment.

In addition, the controller 110 may change the signal shape of the carrier signal to adjust (eg, increase or decrease) the duration of the logic high level of the PWM signal for each signal level period of the audio signal.

Referring to FIG. 6 , the carrier signal output according to the control of the controller 110 may have a signal shape for increasing or decreasing the duration of the logic high level of the PWM signal for each signal level period. FIG. 6 shows an enlarged portion of the 1/4 time period of the carrier signal. That is, the carrier signal shown in FIG. 6 corresponds to 1/4 time period 340 of the carrier signal 310 in FIG. 3 . In addition, in order to describe the change of the signal shape of the carrier signal by the controller 110, a single gain carrier signal 620 is further shown with the signal shape not changed.

The controller 110 may change the signal shape of the carrier signal 610 to reduce the logic high level of the PWM signal in the first time period from 0 to V0 (in which the level of the audio signal is zero-crossing). flat duration. In general, there is a lot of noise during a period in which the signal level is almost 0 (ie, zero crossing). Accordingly, the controller 110 may change the signal shape of the carrier signal to reduce the gain in the period in which the code is transformed.

Referring to FIG. 6, the controller 110 can control the signal shape of the carrier signal 610 so that the signal level of the carrier signal 610 can have a signal level greater than that of the single gain carrier signal 620 in the first time period when the code is converted. value. Accordingly, the carrier signal generator 210 may output the carrier signal 610 having the signal shape shown in FIG. 6 . Therefore, during the period in which the code from 0 to V0 is converted, the duration of the logic high level of the PWM signal is reduced and output.

That is, the controller 110 may control the PWM unit 120 to generate a carrier signal used as a compressor for reducing a gain value in the first period.

In addition, the controller 110 may change the signal shape of the carrier signal 610 to increase the duration of the logic high level of the PWM signal in the second period in which the level of the audio signal is equal to or greater than V0 level and less than or equal to the V3 level, wherein the V0 level is the upper limit of the first time period, and the V3 level is a predetermined standard level. In the second period from the V0 level to the V3 level, although the volume is increased, the audio signal output device 100 may not perform an operation exceeding the maximum output. Therefore, during the second time period, by increasing the volume, the user's satisfaction with the sound quality may increase.

Referring to FIG. 6, the signal level of the carrier signal 610 is lower than the signal level of the single gain carrier signal 620 in the second period. When an audio signal having a V1 level is input, the carrier signal 610 may increase the duration of the logic high level of the PWM signal by a time period 650 based on the single gain carrier signal 620 . In addition, when an audio signal having a V2 level (i.e., corresponding to the half value of the maximum output signal level V5) is input, the carrier signal 610 can maintain the logic high level of the PWM signal based on the single gain carrier signal 620 Time increases the length of time 651.

That is, the controller 110 may control the PWM unit 120 to generate a carrier signal acting like a booster that increases the gain value in the second period (ie, the intermediate signal level period).

In addition, the controller 110 may change the signal shape of the carrier signal to reduce the duration of the logic high level of the PWM signal in the third period in which the level of the audio signal is equal to or greater than V3.

Referring to FIG. 6, the signal level of the carrier signal 610 is greater than the signal level of the single gain carrier signal 620 in the third period. The lower limit of the third time period may be the above-mentioned predetermined standard level, and the upper limit of the third time period may be the signal level V5 corresponding to the maximum output. For example, when an audio signal having a signal level V5 is input, the audio signal output device 100 may output sound at the maximum volume among sounds that can be output.

When an audio signal having a level V4 is input, the carrier signal 610 may reduce the duration of the logic high level of the PWM signal by a time length 652 based on the unity gain carrier signal 620 .

That is, the controller 110 may control the PWM unit 120 to generate a carrier signal used as a compressor for reducing the gain value in the third period.

As described above with reference to FIGS. 4 to 6 , the audio signal output device 100 changes the signal shape of the carrier signal and generates the carrier signal according to the signal level of the audio signal. Therefore, the gain value may be directly adjusted during generation of the PWM signal without including or using a compressor or a booster as a separate circuit block for adjusting the gain value. That is, by changing the signal shape of the carrier signal and generating the carrier signal, the gain can be directly adjusted during generation of the PWM signal without performing a separate operation of adjusting the gain.

Accordingly, the structure of the audio signal output device 100 can be simplified, and a PWM signal having a relatively quickly adjusted gain value can be generated. Furthermore, power consumption can be reduced by eliminating power consumption in a separate circuit block for adjusting the gain value.

As described above with reference to FIG. 6 , the audio signal output apparatus 100 may remove noise, and may increase volume by reducing or increasing the duration of the logic high level of the PWM signal for each individual signal level.

Also, by changing the signal shape of the carrier signal, the audio signal output device 100 can be controlled not to perform an operation exceeding the maximum output. Therefore, the audio signal output device 100 can be prevented from being destroyed, and the operational reliability of the audio signal output device 100 can be improved.

FIG. 7 illustrates a detailed block diagram of an audio signal output device 700 corresponding to the audio signal output device 100 of FIG. 1 according to another exemplary embodiment.

Referring to FIG. 7 , an audio signal output device 700 may further include a loop filter 740 and a speaker unit 750 in addition to the audio signal output device 100 of FIG. 1 . The controller 710, the PWM unit 720, and the switching power supply unit 730 respectively correspond to the controller 110, the PWM unit 120, and the switching power supply unit 130 that have been described with reference to FIGS. 1 and 2, and thus their detailed descriptions will be omitted.

The speaker unit 750 receives the PWM signal amplified by the switching power supply unit 730, converts the PWM signal into an audible sound signal, and outputs the sound signal.

The loop filter 740 detects the output level of the amplified PWM signal output from the switching power supply unit 730 . In addition, the loop filter 740 monitors whether the output level of the amplified PWM signal exceeds the maximum output level of the audio signal output device 100 .

The controller 710 receives the monitored results from the loop filter 740 . In addition, when it is determined that the output level of the amplified PWM signal exceeds the maximum output level, the controller 710 controls the PWM unit 720 to change the signal shape of the carrier signal to reduce the duration of the logic high level of the PWM signal. For example, the controller 710 may limit the level of the audio signal to the maximum output level in a period in which the audio signal exceeds the maximum output level. In addition, the controller 710 can control the PWM unit 720 to generate a carrier signal for reducing the gain value. The generation of the carrier signal for reducing the gain value has been described with reference to FIG. 5, and thus a detailed description thereof is omitted.

FIG. 8 illustrates a flowchart of a method of outputting an audio signal according to an exemplary embodiment.

Referring to FIG. 8, the method according to an exemplary embodiment includes detecting a level of an audio signal received by the controller 110 (operation 810).

According to the detected level of the audio signal, the signal shape of the carrier signal is changed to increase or decrease the duration of the logic high level of the PWM signal, and the carrier signal is generated (operation 820). For example, the controller 110 may output a change control signal for changing the signal shape of the carrier signal to the PWM unit 120, and the PWM unit 120 (specifically, the carrier signal generator 210) may output the change control signal according to the change control signal output by the controller 110. Generate a carrier signal.

Signal levels of the carrier signal and the audio signal are compared to generate a PWM signal (operation 830). Operation 830 may be performed in the PWM unit 120 (specifically, in the PWM signal generator 220).

The power of the PWM signal is amplified and the amplified PWM signal is output (operation 840). Operation 840 may be performed by the switching power supply unit 130 .

In addition, the method according to the present embodiment may further include changing the amplified PWM signal into a sound signal and outputting the sound signal (operation 850). Operation 850 may be performed by the speaker unit 750 .

The technical spirit and operational configuration of the method of outputting an audio signal according to the above-described exemplary embodiments are the same as or similar to those of the audio signal output device described above with reference to FIGS. 1 to 7 , and thus a detailed description thereof will be omitted.

Although not limited thereto, exemplary embodiments can be embodied as computer readable codes on a computer readable recording medium. The computer readable recording medium is any data storage device that can store data which can be thereafter read by a computer system. Examples of the computer readable recording medium include read only memory (ROM), random access memory (RAM), CD-ROM, magnetic tape, floppy disk, and optical data storage devices. The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. Also, the exemplary embodiments can be written as computer programs, which are transmitted through computer-readable transmission media such as carrier waves, and received and implemented in general-purpose or special-purpose digital computers that execute the programs. Additionally, one or more units of the audio signal output device may include a processor or a microprocessor executing a computer program stored in a computer readable medium.

While exemplary embodiments have been particularly shown and described above, it will be understood by those of ordinary skill in the art that changes in form and details may be made without departing from the spirit and scope of the inventive concept as defined by the claims. Make various changes.

Claims (23)

1. a kind of audio-frequency signal output apparatus, including：

Controller, based on the signal level of audio signal, controls PWM units and changes the signal shape of carrier signal to adjust PWM The persistent period of the logic high of signal；

Pulse width modulation (PWM) unit, from controller the change control letter for changing the signal shape of carrier signal is received Number, carrier signal corresponding with the signal shape for changing is produced, by the signal electricity of the signal level of carrier signal and audio signal It is flat to be compared, and pwm signal is produced based on result of the comparison；

Switching power supply, amplifies the pwm signal produced by PWM units and the pwm signal for exporting amplification.

2. audio-frequency signal output apparatus as claimed in claim 1, wherein, when the signal level of audio signal is higher than predetermined mark During quasi- level, the logic high that controller control PWM units change the signal shape of carrier signal to reduce pwm signal is held The continuous time.

3. audio-frequency signal output apparatus as claimed in claim 1, wherein, when the signal level of audio signal is less than predetermined mark During quasi- level, the logic high that controller control PWM units change the signal shape of carrier signal to increase pwm signal is held The continuous time.

4. audio-frequency signal output apparatus as claimed in claim 1, wherein, controller also includes：Memory element, store with regard to The information of the signal shape of the corresponding carrier signal of signal level of audio signal.

5. audio-frequency signal output apparatus as claimed in claim 1, wherein, controller control PWM units change carrier signal Signal shape, with for each signal level time period adjustment of the audio signal with different audio signal level scopes The persistent period of the logic high of pwm signal.

6. audio-frequency signal output apparatus as claimed in claim 5, wherein, in the first time period of the zero passage that audio signal occurs In, controller control PWM units change the signal shape of carrier signal with reduce pwm signal logic high it is lasting when Between.

7. audio-frequency signal output apparatus as claimed in claim 6, wherein, it is equal to or more than the in the signal level of audio signal In the upper limit of one time period and the second time period less than or equal to predetermined fiduciary level, controller control PWM units change Become the signal shape of carrier signal to increase persistent period of the logic high of pwm signal.

8. audio-frequency signal output apparatus as claimed in claim 7, wherein, it is equal to or more than institute in the signal level of audio signal In the 3rd time period for stating predetermined fiduciary level, controller control PWM units change the signal shape of carrier signal to reduce The persistent period of the logic high of pwm signal.

9. audio-frequency signal output apparatus as claimed in claim 1, also include：Loop filter, detects the pwm signal of amplification Output level, and monitor whether the pwm signal of amplification exceedes Maximum Output Level.

10. audio-frequency signal output apparatus as claimed in claim 9, wherein, controller receives the knot of monitoring from loop filter Really,

Wherein, when the signal level of the pwm signal for amplifying exceedes Maximum Output Level, controller control PWM units change load The signal shape of ripple signal is reducing persistent period of the logic high of pwm signal.

11. audio-frequency signal output apparatus as claimed in claim 1, also include：Speaker, receives the pwm signal for amplifying, and will put Big pwm signal changes into acoustical signal, and exports acoustical signal.

A kind of 12. methods of exports audio signal, methods described includes：

The signal level of detection audio signal；

The carrier signal of the signal shape for producing the signal level with the audio signal for being based on detection and changing, to adjust pulse The persistent period of the logic high of width modulated (PWM) signal；

Compare the signal level of the signal level of carrier signal and the audio signal of detection；

Pwm signal is produced based on result of the comparison；

Amplify pwm signal and export the pwm signal of amplification.

13. methods as claimed in claim 12, wherein, produce and there is the signal level based on the audio signal of detection and change Signal shape carrier signal the step of include：When the signal level of the audio signal of detection is higher than predetermined fiduciary level When, change the signal shape of carrier signal, to reduce the persistent period of the logic high of pwm signal.

14. methods as claimed in claim 12, wherein, produce and there is the signal level based on the audio signal of detection and change Signal shape carrier signal the step of include：When the signal level of the audio signal of detection is less than predetermined fiduciary level When, change the signal shape of carrier signal, to increase the persistent period of the logic high of pwm signal.

15. methods as claimed in claim 12, also include：Store with regard to corresponding with the signal level of the audio signal of detection The information of the signal shape of carrier signal.

16. methods as claimed in claim 12, wherein, produce and there is the signal level based on the audio signal of detection and change Signal shape carrier signal the step of include：Change the signal shape of carrier signal, with for believing with different audio frequency The persistent period of the logic high of each signal level time period adjustment pwm signal of the audio signal of number level range.

17. methods as claimed in claim 16, wherein, change carrier signal signal shape the step of include：There is sound In the first time period of the zero passage of frequency signal, change the signal shape of carrier signal to reduce the logic high of pwm signal Persistent period.

18. methods as claimed in claim 17, wherein, change carrier signal signal shape the step of include：In detection The signal level of audio signal is equal to or more than the upper limit of first time period and less than or equal to the of predetermined fiduciary level In two time periods, change the signal shape of carrier signal to increase persistent period of the logic high of pwm signal.

19. methods as claimed in claim 18, wherein, change carrier signal signal shape the step of include：In detection The signal level of audio signal was equal to or more than in the 3rd time period of the predetermined fiduciary level, changed the letter of carrier signal Number shape is reducing persistent period of the logic high of pwm signal.

20. methods as claimed in claim 12, also include：The output level of the pwm signal that detection is amplified, and determine amplification Whether the output level of pwm signal exceedes Maximum Output Level.

21. methods as claimed in claim 20, also include：When it is determined that the output level of the pwm signal for amplifying is defeated more than maximum When going out level, change the signal shape of carrier signal to reduce persistent period of the logic high of pwm signal.

22. methods as claimed in claim 12, also include：The pwm signal of amplification is changed into into acoustical signal and sound is exported Signal.

A kind of 23. methods of exports audio signal, methods described includes：

Produce carrier signal；

Compare the signal level of carrier signal and the signal level of audio signal；

Pulse width modulation (PWM) signal is produced based on result of the comparison；

By the logic high for changing the signal shape of carrier signal according to the signal level of audio signal to control pwm signal Persistent period.